1. Field of the Invention
The invention relates to a method for controlling the on-the-fly splicing of a web wound on a second or new roll, set in rotation, to a web wound on a first or old roll and, more particularly, to a method for controlling such splicing when changing the web wound rolls in a rotary printing press.
2. Description of the Prior Art
A typical prior art method for controlling the on-the-fly splicing of a web wound on a second roll to a web wound on a first roll is carried out in the following manner: the roll carrier containing both rolls is swung from the roll-off (unwind) position into the pasting position, when the first roll reaches a first diameter or circumference value; the second roll is accelerated and its peripheral velocity is made equal to the velocity of the web of the first roll when the first roll reaches a second diameter or circumference value; and a pasting and cutting device is operated for pasting the pasting tip at the start of the web of the second roll to the web running off the first roll and for cutting off the aforesaid web behind the pasted point, when the first roll reaches a third diameter or circumference value.
The aforesaid prior art method is disclosed in German Auslegeschrift DT-AS 1,147,599, DT-AS 1,082,901 and the German Petty Patent DT-GM 1,867,437. As disclosed therein, the individual phases of the roll splicing are initiated as a function of the decrease of the diameter or the circumference of the first roll. In practice, fixed settings of several diameter or circumference values are used for instituting the individual phases and the corresponding control elements are addressed when the first roll reaches the respective set diameter or circumference values. The fixed settings are determined on the basis of empirical values and for safety reasons, the respective fixed settings or starting points are chosen relatively early.
The thickness of the web of the first roll is determined from the area weight given by the manufacturer by means of tables and is also set to a fixed value. Thus, unavoidable thickness changes of the web are not taken into consideration during the splicing procedure. Moreover, the changing of rolls is time consuming and the time of cutting off of the web of the first roll is of insufficient accuracy to avoid having the end diameter of such roll vary over a wide range.
It is, therefore, an object of the present invention to provide a method of the above-described type which permits faster operation and improved accuracy in the end diameter of the first or old roll.